Question about 1999 Hyundai Sonata
My car jerks and vibrates when in drive and i'm holding down the brakes. Its does it more noticeably whenever the ac is on
Sounds like it's misfiring. You've most likely got a fouled sparkplug(s). An engine that's not running on all cylinders will vibrate badly and get worse the faster you go. The AC will make the engine work harder therefore, increase the vibration. Decreased fuel economy is also a byproduct of a poor tuned engine.
If the plugs are good and you don't notice worsening fuel economy, the other main cause of your issue is a bad motor mount. This is noticeable when putting the car in gear you will feel a bump or "thunk". I'd definitely check the plugs/wires first. Best of luck with your problem.
Posted on May 14, 2009
Hi, i recommend changing the fuel filter and pump as well. this is common when you have restricted fuel flow through the fuel lines due to a clogged filter and faulty pump. I would also recommend having the injectors purged with a fuel additive called Techtron injector/tank treatment. this will clean out the carbon build up in the intake and it will also clean the injectors as well.
I recommend applying a tune up by adding new wires and plugs. this is extra maintenance and it is optional. i do recommend applying this along with the above suggestions.
Please rate and have a great day:)
Posted on May 14, 2009
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Posted on Jan 02, 2017
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